Knife and knife holder assembly in veneer cutting machines



Aug. 19, 1952 E. H. MERRITT KNIFE AND KNIFE HOLDER ASSEMBLY IN VENEERCUTTING MACHINES Filed Aug. 25, 1948 w n f m, rm mm M I M N m. wp

A TTORNEX Patented Aug. 19, 1,952

KNIFE AND KNIFE HOLDER ASSEMBLY IN VENEER CUTTING MACHINES Ericsson H.Merritt, Lockport, N. Y.,'assignor, by

mesne assignments, to Solem Machine Company, Rockford, 111., acorporation of Illinois Application August 25, 1948, Serial No. 46,083.

- 5 Claims.

This invention relatestothe art of cutting and slicing wood veneer; moreparticularly it relates to an improved knife-andknife holder combinationto be used with veneer cutting and slicing equipment.

In general practice rotary veneer is produced by revolving a log againsta knife whose length is equal to or in excess of the length of the logbeing cut. Sliced veneer is produced by clamping a flitch toareciprocating table and moving the table with the-flitch"past theknife. 'Ateach stroke a sheet of veneer is cut from the iiitch. In eachof the described veneer cutting opera? tions, to prevent the ,wood fromsplitting ahead of the knife, a pressure plate is provided to'applypressure to the log just'ahead of the knife. Thus, the ribbon of veneersevered from the log by the knife is actually extruded through the slotformed by the knife and the pressure plate. The crosssection of thisslot isslightly less than the thickness of veneer'being cut. To cutsmooth uniform.

thickness veneer, the slot must be of uniform cross-section and haveparallel edges. Furthermore, in the case of rotary veneer the bottomedge of the slot formed, by the edges of the knife must be in accurateparallel relationship to the axis of rotation of the logand the top ofthe slot formed. by the pressure plate must be in accurate parallelrelationship to'the knife edge. is not unusual to cut veneer as thin asfifteen thousandths of an inch in thickness, 'it is obvious that thetolerances to which the knife must be set'are extremelynarrow. 1

Veneer knives are composite structures generally varying in sizefrom {2inch to inch thick, usually 6 inches to? A; inches wide when new, andvaryingin length from 24inches to 200 inches.

Since it i r Slots are usually provided for bolts used to at-' not tomention the loading incident to cutting.

As the knife becomes narrower due to grinding,

sharpening operation on the knife, due to the stresses introduced by theveneer cutting operation, it is often necessary to force the knife to.assume a straight line. The bevel of'the knifeis ground until a sharpcutting edge is produced which is a straight line within the limits ofaccuracy of the grinder and the perfection of the plane of the face ofthe knife. This grinding operation to a certain extent releases many of[the stresses which were formed in the knife during the .cuttingoperation. When the knife is released from the grinder clamps which holdthe knife rigidly in place during'the grinding operation, it immediatelyassumes its natural shape and the cutting edge'is no longer a-truestraight line. Accordingly'when this knife is attached to the knifecarriage in the veneencutting machine, it must be adjusted higher tocompensate for the width lost in the grinder and also it must :be forcedby local adjusting screws provided in the knife, carriage, to take-sucha shape that the cutting edge withbe a true straight line parallel tothe axis of rotation of the log. This is a time consuming operationrequiring a highdegree of skill. Thus, according to the method aspracticed heretofore'of handling veneer cutting knives, a precisionalignmentof theknife is the positioning of the knife in a veneer cuttingmachine so that precision alignment is obtained with a minimum amount oflocal adjusting.

Another object of this invention is to provide a veneer cutting knifeand knife holder assembly which when precision ground will be in perfectalignment without. further adjustment when placed in the veneercuttingmachine.

It is also an object of this invention to provide an improved knife andknife holder assembly for a veneer cutting machine which eliminates allbut a small fraction of the time required to change this deflectionmaterially increases. Thus, the

a knife in a veneer lathe or a veneer slicer.

Further objects will become apparent from the description of theinvention and the claims.

These objects are accomplished by means of the applicants inventionwhich provides an accurately machined rigidsteel beam, called theholder, to which a cutting knife is adjustably attached. The veneercutting knife and knife holder are removable as a unit from the veneercutting machine. The holder'is so constructed as to have a moment ofinertia sufficiently great with respect to the knife to resistdeflection of the knife caused by unbalanced stresses therein.

Slots are provided in the holder for rbolts which are threaded into theknife holding the knife rigidly in place. Holes are also provided inboth the holder and the knife attached thereto for the purpose ofsecurely bolting the unit to the veneer cutting machine. Push and pulladjusting screws are provided in thebottom of the holder to facilitateadjustment of the knife in the holder. The machined surfaces of theholder and their cooperative machined surfaces on the veneer cuttingmachine are so constructed as to maintain a fixed relationship betweenthe surfaces and the line of contact between the cutting ed eof' theknife and the log or fiitch.

With such a construction, during the sl'iarpe'ning operation, the dullor nicked knife, together A with its holder, are 'removed'as a unit fromthe lathe or the slicer. At the grinding wheel, the

. knife is adjusted with respect to the holder to a distance equal tothe amount of knife which must be ground away to produce a new perfectedge.

Thfebfevel' of the knife while rigidly clamped in its holder; is grounduntil the distance from the new 7 edge 'to' the locating. surfaces onthe holder is the correct distance to bring the knifehdge to the properposition in the veneer lathe or slicer. The knife and: knife holder arethen removed from the grinder, and, due to the moment of inertia of Ithek'nife holder; the knife edge remains a straight I line and does'notbow or otherwise deflect due to the internal stresses in the. knife. Onreplacing the resharpened knife and its holder in the veneer cutting or.slicing machine so that the 10- eating surfaces of theiknife holder arein contact with their cooperative locating surfaces in thecuttingmachin'e, the knife edge is automatically in correct adjustmentrequiring no further manual local adjusting.

5 The'invention' will be more clearly understood from the followingdescription wherein:

- Figure 1 isthe front "elevation of a fragmentary length of the knifeand knife holder assembly'of thisinvention.

Figure 2 is a transverse section of the knife and knife holder assemblyof this invention taken on line 2 -2 of Figure l, supported in aconventional 'mannerin a veneer lathe. I

' Figure 3 is a transverse section of the knife and knife holder ofthisinvention taken on line 33 of Figure 1.

- The knife holder' l is an accurately machined rigid steel beam towhich the adjustable veneer knife 5 is attached. Surface 6 of the knifeholder and surface 1 of the knifeholder seat are accumating with aplurality of oval shaped slots I4.

The holes l3 are so ledged to accommodate clamping bolts I5 whereby theknife holder 3 and knife 5 may be rigidly attached to back plate I 6 insuch a manner that surface 6 is exactly positioned on surface 7.Veneerknife 5 contains a plurality of slots I! so positioned and of sucha size to permit an unobstructed passage of bolt l5. Alternatingwith'slots ,I'! onkm'fe 5 are a plurality of rows of threaded holes l8,each row of holes consisting of three and being on a center lineperpendicular to the length of knife edge, and

. 4 each hole being of such a size to accommodate bolt 19 when placedthrough slot IA of the knife holder, with slot 14 being so ledged topermit knife 5 to be rigidly attached to holder 4 by tightening bolt [9,and adjusting by means of push screw 20 or pull screw 2|, for which a.threaded hole and a clear hole are provided in holder 4, respectively.Screws 20 and 2 l are so constructed that they do not extend beyondsurface 6 of holder 1.

In operation, log 8 is rotated against knife edge 22 cutting a. sheet ofveneer which is extruded through. the slot one side of which is formedby the edge of pressure plate 23, which is held in place by pressureplate holder 24, and the other side of" which is formed by the cuttingedge 22 of veneer =knife'5. 0n requiring sharpening, bolts l5 areremoved and knife holder 4 and veneer sharpened knife edge 22'wi1l beequal tofthe preciselyset and predetermined 'distance' on the lathe.Inasmuch as the knife holder 4 has a sufiicient moment of inertiawithrespect to the knife to resist deflection ofthe knife due to thestressesand' strains setup in the knife during the cutting and grindingoperations, when the knife holder and the knife which has beenaccurately aligned at the grinding operation is repositioned in thelathe, no further adjustment of the knife 5 is required. Therefore,since the distance from surface 1 to knife edge 22' is constant, andsince this distance is accurately set in the grinding op- I eration, andsince the holder is of such a size to resist deflections of the knifedue to strains, all

that remains after the grinding operation ismerely the repositioning ofthe knife and knife holder assembly in the veneer lathe. Thus, in-

' stead of the procedure aspracticedheretofore of requiring'two accuratealignments of the knife, one during the grinding operation and anotherduring the repositioning of'the sharpened: knife in the lathe, only onealignmentisneces'sary, thereby greatly reducing the requirements ofhighly skilled techniques;

According to heretofore practiced techniques, a dull or nicked veneerknife requiring resharpen ing is removed singly from the cuttingmachine. An experienced grinder then grinds or resharpens the knifeforcing the knife edge by local adjustment to assume a true straightline. The grinder then releases the knife from the grinder carriage and.returns the knife to the slicer or veneer lathe. However, on releasingthe knife from the grinder; due to the unbalanced stresses in the knifeand the lack of rigidity of the knife blade, the true straight cuttingedge is lost due todeflec- Consequently, when this knife is again tions.positioned in the cutting lathe or slicer, realign ment by localadjusting'of the knife is again necessary toforce the cutting edge ofthe knife intoa" true straight line. Such an aligning and adjustingoperation requires a skilled craftsman. With the knife and knife holderassembly of this -inven tion, it is this second local adjustment of theknife that is eliminated. Inasmuch as the cut ting edge has beenproperly aligned during the grinding operation and is rigidly held inplace'by f the holder that has a sufficient moment of inertia to resistsubsequent deflections of the knife and that such holder is soconstructed with regard to the veneer cutting machine as to maintain afixed relationship with the line of contactbetween the cutting edge'ofthe knife and the log or flitch, further adjustment of the knifeisunnecessary whenthe knife and its holder is repositionedin theveneercutting machine. I

' What is claimed is: i

1;,In a veneer cutting machine comprising a carriage adapted for rigidlysupporting the holder of a veneer cutting knife, said carriage includinga back plate, a knife and knife holder combination assembly installableand removable as a unit on and from the carriage respectively, meansadjustably attaching said knife to said knife holder on that side of theholder adapted to face the back plate, said knife holder having a momentof inertia sufiiciently great to resist defiection of the attachedknife, said knife holder having accurately machined locating surfacescooperative with accurately machined locating sur faces On the knifeholdercarriage whereby the distance of the cutting edge of said knifefrom the said locating surfaces on the knife holder carriage may beaccurately set and maintained by said adjustable attaching means beforesaid assembled knife holder and knife is positioned on the carriage, andmeans fastening said assembled knife holder and knife to the back plateon the carriage comprising bolts extending from said knife holder to theback plate through aligned apertures in said knife and which also serveto clamp said knife between said knife holder an back plate.

2. In a veneer cutting machinacomprising a,

of a veneer cutting knife, the carriage including an elongated backplate, the improvement consisting of a knife and knife holdercombination assembly installable and removable as a unit on and from thecarriage respectively, said knife and knife holder being both elongated,like the back plate, said knife holder having accurately machinedlocating surfaces arranged for abutment with accurately machinedlocating surfaces on the carriage, a plurality of bolts, each of whichextends through aligned apertures in said knife holder and knife, one ofsaid aligned apertures being slotted for adjustably securing said knifeto said holder on that side thereof adapted to face the back plate, anda plurality of other bolts each of which extendsthrough alignedapertures in said knife holder and knife and into the back plate forrigidly securing the assembled knife and knife holder to the back plateand clamping the knife between the holder and back plate.

3. In a veneer cutting machine, comprising a carriage adapted forrigidly supporting the holder of a veneer cutting knife, the carriageincluding an elongated back plate, the improvement consisting of a knifeand knife holder combination assembly installable and removable as aunit on and from the carriage respectively, said knife and knife holderbeing both elongated like the back plate, said knife holder havingaccurately machined locating surfaces arranged for abutment withaccurately machined locating surfaces on the carriage, a plurality ofbolts, each of which extends through aligned apertures in said knifeholder and knife, one of said aligned apertures being slotted foradjustably securing said knife to said holder on that side thereofadapted to face the back plate, said bolts when loosened engaging saidknife-forlocal adjustment of mage;

tudinally spaced portions of theknife'in'th-plane thereof, and 'aplurality of other-"bolts each of which extend through alig'ned?apertures m said knife holder and knifeand -into* "the' back plate forrigidly securing the assembled knifea nd knife holder to the back plateand clamping the knife between the holder and 1 back plate.

4. In a veneer cutting machine, comprising a carriage adapted forrigidly supporting the holder of a veneer cutting knife, the carriageincluding an elongated back plate, the improvement consisting of a knifeand knife holder combination assembly installable and removable as aunit on and from the carriage respectively, said knife and knife holderbeing both elongated like the back plate, said knife holder havingaccurately machined locating surfaces arranged for abutment withaccurately machined locating surfaces on the carriage, a. plurality ofbolts, each of which extends through aligned apertures in said knifeholder and knife, one of said aligned apertures being slotted foradjustably securing said knife to said holder on that side thereofadapted to face the back plate, said bolts when loosened permittingadjustmentas to elevation of the knife relative to the holder as awhole, a plurality of parallel push screw disposed in the plane of andbehind the knife and threaded in the holder at longitudinally spacedpoints and abutting the plane of the push screws entered with freedom toturn in holes provided therefor in the holder and threaded in holesprovided therefor in the knife at longitudinally spaced points betweenthe push screws for local adjustments of longitudinally spaced portionsof the knife in the opposite direction to that of the adjustmentsafforded by said push screws, and a plurality of other bolts each ofwhich extends through aligned apertures in said knife holder and knifeand into the back plate for rigidly securing the assembledknife andknife holder to the back plate and clamping the knife between the holderand back plate.

5. Ina veneer cutting machine, comprising a carriage adapted for rigidlysupporting the holder of a veneer cutting knife, the carriage includingan elongated back plate, the improvement consisting of a knife and knifeholder combination assembly installable and removable as a unit-on andfrom the'carriage respectively, said knife and knife holder being bothelongated like the back plate, said knife holder having accuratelymachined locating surfaces arranged, for-abutment with accuratelymachined locating surfaces on the carriage, a plurality of bolts, eachof which extends through aligned apertures in said knife holder andknife, one of said aligned apertures being slotted for adjustablysecuring said knife to said holder, said bolts when loosened permitplaneof the push screws entered with freedom to turn in holes providedtherefor in the holder andthreafied iniholes'iprovfided therefor in theY e 1 knife at Jang-itudinamrspaced points 'between'the l FERENCES CITEDP screws mal'fidjustments longitudi" The following references are 01'record in the nally spaced portions of theknife in the opposite m f thispatent;

tobhagb the adjustments affordedby- 5 said push screws,; and a pluralityof'other bolts, N E STATES PATENTS extending through'apertures in saidknife holder' N m r Name Date into the back plate'for, rigidlysecurin'githe, as- 835,156 Fitts Nov. 6, 1906 sembled knife and knifeholder to the back plate. 1,890,532 7 K058, 1386- 3, 1932 e I r v n h 1V Y 10 1,957,166 Hartzell "May1.',1934

,' 1 ERICSSONiH. MERRITT. 2,337,407 Otterslgnd Dec. 21,1943

